process.nextTick() and setImmediate() are two ways to schedule a callback function to be executed in the next iteration of the event loop. However, there are some differences between them:

• process.nextTick() runs the callback before any other I/O events (including timers) that are scheduled for the current iteration of the event loop. This means that process.nextTick() is generally used to perform non-blocking operations that need to be completed as soon as possible.

• setImmediate() schedules the callback to be run after the current iteration of the event loop is completed. This means that setImmediate() is generally used to schedule non-blocking operations that do not need to be run immediately, but can be run in the next iteration of the event loop.

console.log('Start');

setImmediate(function() {
  console.log('Inside setImmediate');
});

process.nextTick(function() {
  console.log('Inside nextTick');
});

console.log('End');

Start
End
Inside nextTick
Inside setImmediate